The In Vivo Imaging Core of the Comparative Bioscience Center is seeking to upgrade our current high- frequency micro-ultrasound instrumentation. The proposed VisualSonics Vevo 2100 high frequency micro- ultrasound upgrade will transition an existing Vevo 770 micro-ultrasound into a dynamic research tool that meets the research needs of six laboratories with NIH-funded projects. Although the research applications for our major and minor users are diverse, there is a common need to carry out noninvasive longitudinal studies using murine disease models. The proposed upgrade, the VisualSonics Vevo 2100 micro-ultrasound platform, will address an institutional need for advanced in vivo imaging technology that can be used to optimally enhance cardiovascular studies, acute and longitudinal cancer studies, the characterization of murine models of liver disease, as well as muscle ablation and regeneration studies. The upgraded micro-ultrasound platform contains an array of new and enhanced features: Color Doppler (the ability to study blood flow directionality and velocity), the ability to utilize nonlinear contrast agents, advanced analysis software such as VevoStrain (capable of detecting cardiovascular wall motion abnormalities), adjustable focal depth and superior resolution (features which aid in tumor detection), the ability to perform a split screen analysis of micro-ultrasound images (features which enhance the repeatability of data obtained over longitudinal studies), as well as the ability to use factory and customized presets which will make the instrumentation simpler, more efficient, and more readily accessible to new users. The upgraded instrument will be maintained as a shared imaging resource within the Comparative Bioscience Center and will be supported by the institution for the lifetime of the instrument. At The Rockefeller University the Vevo 2100 micro-ultrasound upgrade will be used to assist in the study of the hepatitis C virus and liver disease that occurs as a sequela to infection with the hepatitis C virus, the study of muscle ablation and regeneration, as a platform to enable xenotransplantation of human embryonic stem cells in the mouse embryonic cortex and spinal cord, to enhance the study of primary and metastatic neoplastic diseases, including skin and hair tumors, and as an imaging tool to study rodent cardiovascular disease models of fibrocalcific aortic valve stenosis and myocardial infarction with the goal of developing new therapies for heart attack or stroke victims.